1. Field of the Invention
The invention relates to a composite pane having a film laminate with the features of the disclosed composite pane.
2. Description of the Background
Composite panes which are intended for installation in vehicle sliding and lifting roofs or else as rear side windows and windscreens for vehicles are known, which are composed essentially of two rigid panes of glass or plastic, and of adhesive films which adhesively connect these two rigid panes to one another. An adhesive film whose bulk is coloured is often used in order to absorb a portion of the light which passes through the composite pane when in the installed state. The acoustic behaviour (silencing) as well as the UV resistance of the final assembly are improved by combination with an uncoloured adhesive film which is clearly transparent in its own right in the final stages. For the latter purpose, the untoned adhesive film faces the incident light or solar radiation (located on the outside) when the composite pane is in the installed state. It absorbs the majority of the incident UV radiation, which could change the colour of the coloured adhesive film in the long term.
The two adhesive films are fused on virtually completely during the final connection of the layers for this composite pane in an autoclave process at about 130 to 150° C. The finished composite pane exhibits a clearly perceptible inhomogeneous cloudy colouring when it is looked through, however, so-called “orange skin”. It has been found that the rough and wavy surfaces of the films on the boundary surface between the clear and the coloured adhesive film leads to non-uniform flow phenomena in the autoclave, and to thickness fluctuations, resulting from this, in the films, whose thickness was approximately uniform before being fused, to be precise, irrespective of whether the two films which had been laminated on to one another were originally of the same thickness, or of different thicknesses.
The roughness and corrugation of the film surfaces are on the one hand unavoidable during production, but on the other hand, they contribute to reliable venting of the initial assembly when a reduced pressure is applied. Air which is enclosed between the layers has to be removed, as is known, and in the process flows away through the channels formed by the surface structures.
Composite panes are also known in which a further thermoplastic film, generally composed of PET (polyethyleneterphthalate) is laminated in between two adhesive films in order to increase the thermal insulation, and is itself provided with a coating (which contains metal) which reflects infrared waves. A film composed of a PET-PMMA co-extrudate or co-laminate can also be used without any metal components for the same function (known by the product name 3M® SRF “solar reflecting film”).
The problem of different colouring and mixing of the adhesive films does not, of course, occur with these film laminates—with adhesive films of the same colour.